A 



JOURNAL 



OF 



NATURAL PHILOSOPHY, CHEiMISTPiY, 



AND 



THE ARTS. 



MARCH, 1810. 



ARTICLE I. 



On Aerial Natigation. Bi/ Sir George Cay ley, Bart, 



{Continued from page Q-]. J 



Bromptout Dec. 6t/>, I8O9. 



OT having sufficient data to ascertain the exact degree Propelling 

 of piopeiHntj po^er exerted by birds in the act of ftviiior j^ po^^'c not '"' 

 . -11 r 1 • r • • ^= exactly csO- 



is uncertain what degree ot energy may be required in this culaicd. 



respect in vessels for tierial navigation : yet, when we cousin 

 d^r the many huodred n)iies of continued flight exerted by 

 birds of passage, the idea of its being only a small effort is 

 greatly corroborated. To apply the power of the first mover 

 to the greatest advantage in producing this effect, is a very 

 material point. The mode universally adopted by nature is 

 the oblique waft of the wing. We have only to choose choice be 

 between the direct beat overtaking the velocity of the cur- tween the di- 

 rent, hke the oar of a boat; or one, applied like the wing, [k[ue stroke , 

 ia bocne assigned degree of obliquity to it. Sunj)ose 35 feet y u •, , 

 per second to be the velocity of an aerial vehicle, the oar quisire forthe 

 must be moved with this speed previous to its being able to '^"^^'^' *^'o!'^*' 

 receive any resistance; then, if it be only required to obtain 

 a presure of xV^h of a potmd upon each square foot, it must 

 exceed the velocity of the current 7-5 feet per second. 

 Vol. XXV. No. 101 — Mar. 1810. M Hence 



